Mathematics - Class ...

Key Points

1. Divisibility by 2, 5 and 10 can be seen by just the last digit.

2. Divisibility by 3 and 9 is checked by finding the sum of all digits.

3. Divisibility by 4 and 8 is checked by the last 2 and 3 digit respectively.

4. Divisibility by 7 - Double the last number of the given number and then subtract it from the rest of the number left in the given number. If the answer we get is either 0 or any number divisible by 7, then the given number is divisible by 7.

5. Divisibility of 11 is checked by comparing the sum of digits at odd and even places.

6. If two numbers are divisible by a number then their sum and difference are also divisible by that number.

7. If a number is divisible by another number then it is divisible by each of the factors of that number.

8. If a number is divisible by two co-prime numbers then it is divisible by their product also.